The present invention pertains to fuel injection pumps. Fuel injection pumps are well known for supplying fuel to the cylinders of an internal combustion engine.
Conventional fuel injection pumps of the type under discussion include a housing in which a cylinder is inserted, guiding in the interior thereof a reciprocally movable and rotational piston which operates as a fuel distributor. The lower end of the piston extends into the pumps suction chamber while its upper end face together with the closing member encloses a pump operation chamber.
German patent publication DE-OS No. 2,503,300 discloses a fuel distributor injection pump, in which the pump piston is arranged in the interior of the cylindrical sleeve or bush. This sleeve at the outer periphery thereof is formed with a partially circular groove, through which a fuel supply passage, opened into that groove and closable by an electromagnetically actuated shut-off valve member, is connected simultaneously with a plurality of fuel-filling openings which open into the interior of the sleeve. The arrangement of these filling openings corresponds to a uniform distribution of the longitudinal grooves provided in the pump piston. In order to maintain the dead volume spaces between the valve-closing member in the fuel supply passage and the mouth of each filling opening in the cylindrical sleeve as small as possible the partially circular groove extends up to two or three filling openings. The above mentioned German patent corresponds to U.S. Pat. No. 4,059,369, the entire disclosure of which is incorporated herein by reference.
It has been known that the presence of a dead space is particularly disadvantageous in respect to the dosing control of the amounts of the injected fuel when this dead space is large in relation to the injected amount of fuel. A specifically disadvantageous effect occurs at the low number of revolutions of the motor. However, it has been required that the smallest possible fluctuations be allowed to obtain a low-roughness running of the internal combustion engine and a favorable exhaust gas composition. In the mostly fast-running self-igniting internal combustion engines (diesels) at the present time, the opening cross-section formed between the fuel supply line and the pump operation chamber in the fuel injection pump, operated at a high number of revolutions, must be during the suction cycle, as large as possible so that with only short suction cycles a sufficiently large opening cross-section would be available, which would ensure a sufficient filling of the pump operation chamber with fuel. Therefore in the known device a plurality of filling openings are provided, which are connected to each other by the partially circular groove.
In the distributor fuel-injection pumps, which with the aid of the valve provided in the fuel supply passage must be set to a zero-feed position so that the internal combustion engine is brought to a standstill, the dead space has a negative effect specifically when one deals with the distributor fuel-injecting pump which serves to supply fuel to five or more cylinders of the internal combustion engine. A reliable shut-down of the internal combustion engine of the above-described conventional construction is then impossible.